Fuel cells have been identified as a relatively clean and efficient source of electrical power. Alkaline fuel cells are of particular interest because they operate at relatively low temperatures, are efficient and mechanically and electrochemically durable. Acid fuel cells and fuel cells employing other liquid electrolytes are also of interest. Such fuel cells typically comprise an electrolyte chamber separated from a fuel gas chamber (containing a fuel gas, typically hydrogen) and a further gas chamber (containing an oxidant gas, usually air). The electrolyte chamber is separated from the gas chambers using electrodes. Typical electrodes for alkaline fuel cells comprise a conductive metal, typically nickel, that provides mechanical strength to the electrode, and the electrode also incorporates a catalyst coating which may comprise activated carbon and a catalyst metal, typically platinum.
In operation, chemical reactions occur at each electrode, generating electricity. For example, if a fuel cell is provided with hydrogen gas and with air, supplied respectively to an anode chamber and to a cathode chamber, the reactions are as follows, at the anode:H2+2OH−→2H2O+2e−;and at the cathode:½O2+H2O+2e−→2OH−so that the overall reaction is hydrogen plus oxygen giving water, but with simultaneous generation of electricity, and with diffusion of hydroxyl ions from the cathode to the anode through the electrolyte. Problems can arise due to changes in the concentration of the electrolyte, as although water is created by the reaction occurring at the anode, water also evaporates at both electrodes.